Promethium history

The second part of the book comprising two chapters (Chapters 12 and 13) is devoted to synthesized elements. In Chapter 12 the reader will be introduced to the synthesis of new elements within the previous boundaries of the periodic system—from hydrogen to uranium (technetium, promethium, astatine, francium). Chapter 13 covers the history of transuranium elements and prospects of nuclear synthesis. 

In total, the rare-earth elements (REEs) represent Vg of all the natural elements and their discoveries spanned 113 years—from 1794 (the discovery of yttrium) to 1907 (the discovery of lutetium). One of REEs, promethium, was prepared artificially much later. The unusual history of REEs is due to their extraordinary properties and, first of all, to their striking chemical similarity. In minerals and ores they are encountered all together at the same time, and it is extremely difficult to break the mixture into constituents. This made the history of REEs very rich in false discoveries with new elements often turning out to be mere combinations of already known ones. Even real discoveries did not always relate to pure rare-earth elements in many cases the newly discovered elements proved later to be a mixture of two or more unknown elements. That is why the widely accepted dates of the discovery of some REEs must be treated with a pinch of salt. 

The history of one rare-earth element is so unusual that it merits individual discussion. Promethium, as it is known now, is practically non-existent in nature (we write practically but not absolutely and the reason for that will be clear later). Event which can only be described as amazing preceded the discovery of element 61 by means of nuclear synthesis. 

But this titanic task was fulfilled in 1968. A group of American scientists including the discoverer of natural technetium P. Kuroda managed to find the natural promethium isotope with a mass number of 147 in a specimen of uranium ore (pitchblende). This was the final step in the fascinating history of the discovery of element 61. 

But in the interval between the syntheses of the isotopes At and At a remarkable event occurred. The scientists from the Vienna Radium Institute B. Karlik and T. Bernert managed to find natural astatine. This was an extremely skillful study straining to the utmost the capacity of radiometry. The work was crowned with success and element 85 was born for the second time. As in the cases of technetium and promethium, we can name two dates in the history of astatine, namely, the year of its synthesis (1940) and the year of its discovery in nature (1943). 

From Figure 17.3 it is clear that the history of discoveries falls into three different periods. The first, about 1800, was the time for the basic discoveries, yttrium and cerium the second, around 1840, resulted in four new elements, erbium, terbium, lanthanum and didymium. Not until the introduction of the spectroscopy in the middle of the 19 century and the development of improved separation techniques did the discoveries enter the third period, 1870-1910. Yet, the last REM, promethium, was not discovered until 1945. Some biographical information about the actual discoverers is given along with the different discovery descriptions below. 

The year 1925 is unique in the history of the discovery of the elements. Rhenium was discovered and accepted, masurium was reported and rejected. Rhenium was the last element discovered with conventional chemical methods. Technetium was the first man-made element, promethium the second (1944). The transuranic elements, discovered in the second half of the 20 century, are aU artificial ... 

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